latency(1) [osx man page]

LATENCY(1)						    BSD General Commands Manual 						LATENCY(1)

NAME

     latency -- monitors scheduling and interrupt latency

SYNOPSIS

     latency [-p] [-h] [-m] [-st threshold] [-it threshold] [-c code_file] [-l log_file] [-R raw_file] [-n kernel]

DESCRIPTION

     The latency utility provides scheduling and interrupt-latency statistics.	Due to the kernel tracing facility it uses to operate, the command
     requires root privileges.

     The arguments are as follows:

     -c code_file
	     When the -c option is specified, it takes a path to a code file that contains the mappings for the system calls.  This option over-
	     rides the default location of the system call code file, which is found in /usr/share/misc/trace.codes.

     -h      Display high resolution interrupt latencies and write them to latencies.csv (truncate existing file) upon exit.

     -m      Display per-CPU interrupt latency statistics.

     -it threshold
	     Set the interrupt latency threshold, expressed in microseconds.  If the latency exceeds this value, and a log file has been speci-
	     fied, a record of what occurred during this time is recorded.

     -l log_file
	     Specifies a log file that is written to when either the interrupt or scheduling latency is exceeded.

     -n kernel
	     By default, latency acts on the default /mach_kernel.  This option allows you to specify an alternate booted kernel.

     -p priority
	     Specifies the priority level to observe scheduler latencies for.

     -st threshold
	     Set the scheduler latency threshold in microseconds.  If latency exceeds this, and a log file has been specified, a record of what
	     occurred during this time is recorded.

     -R raw_file
	     Specifies a raw trace file to use as input.

     The data columns displayed are as follows:

     SCHEDULER		       The number of context switches that fall within the described delay.

     INTERRUPTS 	       The number of interrupts that fall within the described delay.

     The latency utility is also SIGWINCH savvy, so adjusting your window geometry will change the list of delay values displayed.

SAMPLE USAGE

     latency -p 97 -st 20000 -it 1000 -l /var/tmp/latency.log

     The latency utility will watch threads with priority 97 for scheduling latencies.	The threshold for the scheduler is set to 20000 microsec-
     onds.  The threshold for interrupts is set to 1000 microseconds.  Latencies that exceed these thresholds will be logged in
     /var/tmp/latency.log.

SEE ALSO

     fs_usage(1), sc_usage(1), top(1)

Mac OS X							  March 28, 2000							  Mac OS X

Check Out this Related Man Page

hwloc_distances_s(3)					     Hardware Locality (hwloc)					      hwloc_distances_s(3)

NAME

       hwloc_distances_s -

SYNOPSIS

       #include <hwloc.h>

   Data Fields
       unsigned relative_depth
       unsigned nbobjs
       float * latency
       float latency_max
       float latency_base

Detailed Description
       Distances between objects.

       One object may contain a distance structure describing distances between all its descendants at a given relative depth. If the containing
       object is the root object of the topology, then the distances are available for all objects in the machine.

       If the latency pointer is not NULL, the pointed array contains memory latencies (non-zero values), as defined by the ACPI SLIT
       specification.

       In the future, some other types of distances may be considered. In these cases, latency may be NULL.

Field Documentation
   float* hwloc_distances_s::latency
       Matrix of latencies between objects, stored as a one-dimension array. May be NULL if the distances considered here are not latencies.
       Values are normalized to get 1.0 as the minimal value in the matrix. Latency from i-th to j-th object is stored in slot i*nbobjs+j.

   float hwloc_distances_s::latency_base
       The multiplier that should be applied to latency matrix to retrieve the original OS-provided latencies. Usually 10 on Linux since ACPI SLIT
       uses 10 for local latency.

   float hwloc_distances_s::latency_max
       The maximal value in the latency matrix.

   unsigned hwloc_distances_s::nbobjs
       Number of objects considered in the matrix. It is the number of descendant objects at relative_depth below the containing object. It
       corresponds to the result of hwloc_get_nbobjs_inside_cpuset_by_depth.

   unsigned hwloc_distances_s::relative_depth
       Relative depth of the considered objects below the object containing this distance information.

Author
       Generated automatically by Doxygen for Hardware Locality (hwloc) from the source code.

Version 1.7							  Sun Apr 7 2013					      hwloc_distances_s(3)

Linux and UNIX Man Pages

latency(1) [osx man page]

Check Out this Related Man Page